1. Field of the Invention
The present invention relates to the base, drum, and drum mounting unit of a magnetic recording reproducing apparatus in which the drum is mounted in a magnetic recording reproducing apparatus such as video tape recorder or the like.
2. Related Art Statement
In a VTR (video tape recorder), a front loading system is sometimes adopted in which a tape cassette is approximately horizontally loaded into a deck from the front of the deck. In the front loading system, when a tape cassette is inserted into a cassette holder from the front of the deck, the cassette holder moves to a tape loading unit and loads the tape cassette into the tape loading unit. When the tape cassette is set in a predetermined position, a tape in the tape cassette is pulled out by the tape loading unit. The tape loading unit pulls out a tape in a cassette approximately parallel to the surface of a base and winds the tape around a drum.
In a helical scan system, recording and reproducing are performed by obliquely tracing the tape with a magnetic head provided on the drum and hence the drum is mounted on the base at a predetermined angle with respect to the base. The tape loading unit hooks the tape on a pair of tape pulling-out members (hereinafter referred to as “slider”) and pulls out the tape from the tape cassette and moves these sliders to the vicinity of the other end of the drum mounted at the predetermined angle to reel the tape around the drum.
In order to mount the drum to a base at the predetermined angle with respect to the surface of the base, a tilt stand is formed in the same shape and same size as the bottom of the drum and is mounted on the base and the drum is fixed with screws at several points of the end portion of the tilt stand. In this way, the drum is tilted at a predetermined angle with respect to the surface of the base.
A normal-feed press process is adopted for machining the base. The normal-feed press process is also used for various openings and the tilt stand. However, the drum needs to be mounted with extremely high accuracy of the order of several micrometers. In order to enable the drum to be mounted with extremely high accuracy, a screw hole for regulating the position of the drum of the tilt stand portion and a receiving surface thereof for regulating the height of the drum need to be worked by a press process different from the normal-feed press process used for the other portions of the base. That is, those portions need to be press-worked in the state where the base is tilted in correspondence with the tilt angle of the tilt stand.
This presents a problem that the number of processes for machining the base increases. Here, it is also thought that the tilt stand is formed separately by a die casting method, but in this case, the number of processes further increases and the number of parts also increases.
Further, since a structure is adopted in which the drum is fixed with screws at several positions of the brim of the tilt stand, the drum mounting surface of the tilt stand is relatively large in size and the height of the tilt stand is also large. That is, the tilt stand needs to be subjected to a large bending by a press machine, which results in increasing the load of the press machine. Also, the area of an opening made in the base becomes large. This presents a problem that the strength of the base decreases.
Still further, a lead for guiding the tape is formed on the peripheral surface of the drum. There is a possibility that the lead is deformed when the drum is mounted on the tilt stand with screws. Therefore, in order to keep the linearity of the lead with sufficient accuracy, the surface of the tilt stand needs to be worked with extremely high accuracy, but it is very difficult to work the surface of the tilt stand with high accuracy.
As described above, in order to mount the drum with high accuracy, the tilt stand, on which the drum is mounted, needs to be formed by a press process different from the normal-feed press process, which presents a problem that the number of processes increases. Further, this presents problems that the load of the press machine increases and that the strength of the base decreases. Still further, in order to keep the linearity of the lead with sufficient accuracy, the accuracy of the surface of the tilt stand needs to be improved, which presents a problem that it is very difficult to work the surface of the tilt stand with high accuracy.